Platform-based cable exercise device and method

ABSTRACT

A portable exercise device has a base with a pair of contact surfaces suitable to receive the feet of a user, and first and second retracting cables connected to the base. First and second independent springs are biased to retract the cables onto the respective take-up reels. A user-variable, common resistance mechanism includes two brake drums connected to associated take-up reels by one-way clutch mechanisms. Methods of using the device are also disclosed.

FIELD OF THE INVENTION

[0001] The invention pertains to the field of exercise devices and methods, and in particular to exercise devices and methods utilizing cable resistance mechanisms.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] Portable, personal exercise devices are known and available for use. However, prior personal exercise devices are typically cumbersome, expensive or difficult to operate. Therefore, there is a need to provide a portable, personal exercise device that is easy to operate and which provides a number of different exercise options with a high degree of variation in the resistance provided to the user.

[0003] The present invention provides a personal exercise device that overcomes the drawbacks of prior exercise devices. An exercise device constructed according to the present invention comprises a personal, portable cable exercise device with an elongated base and a center enclosure which houses dual, independent take-up reels for exercise cables. The cable take-up reels are connected to a common variable resistance mechanism that can be operated by the user in a simple manner with a high degree of precision. The device includes handles which can be attached to the cables for performing arm exercises, and includes stirrups which can also be attached to the cables for performing leg exercises.

[0004] The variable resistance mechanism of the device, along with the cable return mechanism and associated cable guides are specifically designed to provide for substantially continuous resistance during withdrawal and return of the cables, which provides a desirable smooth and continuous operation of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] For a complete understanding of the above and other features of the invention, reference shall be made to the following detailed description of the preferred embodiments of the invention and to the accompanying drawings, wherein:

[0006]FIG. 1 is a perspective view of a cable exercise device according to the invention, from the front;

[0007]FIG. 2 is a perspective view of a cable resistance mechanism of the device of FIG. 1, from the rear;

[0008]FIG. 3 is a front elevational cross sectional view of the cable resistance mechanism of FIG. 2, taken along line 3-3 of FIG. 1;

[0009]FIG. 4 is a side elevational cross sectional view of the cable resistance mechanism, taken along line 4-4 of FIG. 3;

[0010]FIG. 5 is a close-up front elevational view, taken along line 5-5 of FIG. 2;

[0011]FIG. 6 is a close-up front elevational cross-sectional view, taken generally along line 6-6 of FIG. 4 showing the variable resistance mechanism in a maximum tension position;

[0012]FIG. 7 is a close-up side elevation cross-sectional view, taken along line 7-7 of FIG. 6;

[0013]FIG. 8 is a close-up top plan cross-sectional view taken along line 8-8 of FIG. 6;

[0014]FIG. 9 is a close-up rear elevational cross-sectional view taken along line 9-9 of FIG. 4;

[0015]FIG. 10 is a close-up rear elevational cross-sectional view taken along line 10-10 of FIG. 4;

[0016]FIG. 11 is a view of a method of the invention, showing a user standing on the device using handles attached to resistance cables to perform arm exercises;

[0017]FIG. 12 is a perspective view of a foot attachment accessory of the invention;

[0018]FIG. 13 is a view of a method of the invention, showing a user in a reclined position using the foot attachment accessory to perform leg exercises;

[0019]FIG. 14 is a view of a method of the invention, showing a user standing on the device and using the foot attachment accessory to perform leg exercises;

[0020]FIG. 15 is a view of a method of the invention, showing a user in a reclined position using a multi-purpose accessory attached to the calf to perform leg exercises; and

[0021]FIG. 16 is a view of a method of the invention, showing a user on all fours, using the foot attachment accessory to perform leg exercises.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to FIGS. 1 and 2, a cable exercise device 10 constructed according to the invention provides a compact, portable and inexpensive means to perform a multitude of exercises, at various degrees of difficulty. The basic components of the device include the base 12, an enclosure 28 housing a cable control mechanism 30 and two independent cables 36, 38 held on enclosed take-up reels. Attachment clips 134 are affixed to the ends of the cables for attaching a handle or other accessory of the device 10. The cable control mechanism 30 includes a variable resistance mechanism that is operable by the user via control knob 76 to adjust the resistance provided by the device. While performing exercises, the user extends the cables 36, 38 against the resistive force supplied by the resistance mechanism. The cable control mechanism 30 includes a means to rewind the cables 36, 38 to return the cable to the enclosure.

[0023] The base 12 of the cable exercise device 10 is preferably elongated in shape and is preferably formed of a relatively strong but lightweight metal material such as aluminum. Preferably, the base is substantially planar and is approximately 34 inches long and 8 inches wide, with a cross-sectional thickness of about ¼ to ½ inch. Also, preferably, the base 12 is constructed such that is can support the entire weight of an adult by the extreme ends of the base. Most suitably, the base 12 has a flat bottom surface with non-skid material (e.g., rubber strips) attached thereto.

[0024] Intermediate each end portion 14, 16 of the base 12 and a center portion 22, is a substantially planar contact surface 24, 26 suitable to receive the foot of a user (or another portion of the body such as a hand or leg) thereon. Rigid base handles 18, 20 extend outwardly and preferably slightly upwardly from the end portions 14, 16 so as to allow a person to at least partially grasp the base handle when the base is resting on a flat surface, such as the floor.

[0025] As will be further described below, the device 10 is typically fixed in position during use by applying all or some of the weight of the user to the device via the contact surfaces 24, 26 or the handles 18, 20 (for example, by standing on the device). Therefore, preferably, the contact surfaces 24, 26 are partially covered by a high-friction material to minimize slippage.

[0026] The enclosure 28, which is located on the center portion 22 of the base 12, houses the cable control mechanism 30. The enclosure 28, which is preferably non-load bearing, can be formed of plastic or other lightweight material and includes two side openings 32, 34 through which independent cables 36, 38 pass. In addition, the enclosure 28 includes a center opening 40 through which a shaft for a variable resistance control mechanism passes. As will be discussed in detail below, the enclosure 28 preferably includes a transparent portion aligned to allow the user to view a resistance gauge.

[0027] Referring to FIGS. 2 and 4, the cable control mechanism 30 within the enclosure 28 includes a frame 43 comprised of opposed load-bearing portions 44, 46, which are preferably formed of rigid metal, such as aluminum, steel or the like. A first (rear) portion 44 of the frame 43 has a vertical panel 48 that is preferably substantially rectangular in shape, having a height of about 5 inches and a length of about 10½ inches. A top flange 50 preferably extends outwardly from a top edge 49 of the vertical panel 48, away from a center plane of the device 10. More precisely, the top flange 50 projects outwardly away from a center plane passing through a center line of the base 12, which center plane is aligned perpendicular to a top surface 51 of the base 12. The top flange 50 preferably extends in a normally horizontal plane (i.e., parallel to the base 12). Similarly, a base-contacting bottom flange 54 extends horizontally from a bottom edge 56 of the vertical panel 48 a corresponding distance.

[0028] As with the first portion 44 of the frame 43, the second portion 46 includes a vertical panel 55 and a bottom flange 56 configured similarly to that of the first portion 44. Fasteners rigidly and securely connect the first and second portions 44, 46 of the frame 43 to the base 12 via the respective bottom flanges 54, 56. Preferably, the first and second portions 44, 46 of the frame 43 are spaced such that the vertical panels thereof 48, 55 are separated by about 1¼ inches.

[0029] First and second axles 58, 60 are directed through corresponding holes (not shown) in the first and second panels 44, 46 of the frame 43. A cable take-up reel 62, 64 is mounted on each of the axles 58, 60 such that each take-up reels 62, 64 is disposed adjacent an outward side 65 of the vertical panel 48 of the first panel 44 of the frame 43. The axles 58, 60 about which the take-up reels 62, 64 rotate are preferably aligned substantially parallel to one another and to a “top” surface 51 of the base 12. Further, the axles 58, 60 are spaced about 5 inches apart and are centered vertically on the vertical panel 48 of the first panel 44.

[0030] The take-up reels 62, 64 are about 4 inches in diameter and hold about 80 to 100 inches of cable (or cord) (which preferably is woven nylon cord). Preferably, the take-up reels 62, 64 include flanges 66 extending radially outwardly to contain the cable coiled thereon. The cables 36, 38 are preferably wound around the take-up reels 62, 64 in opposite directions, with the cable leading away from outer sides of the reels, adjacent opposed sides of the cable control mechanism 30. For example, as shown in FIG. 5, take-up reel 62 rotates in a clockwise direction during unwinding, while take-up reel 64 independently rotates counter-clockwise.

[0031] Referring to FIGS. 4 and 10, the cable take-up reels 62, 64 are biased into a fully-wound position by independent rotational springs 174 that serve to recoil the cable onto the respective reels. Each rotational spring is preferably located between the respective take-up reels and the adjacent frame portion 44. Preferably, the maximum bias provided by the rotational springs is relatively low and can be overcome by a cord tension of a few pounds. The cables 36, 38 preferably include stops 37, 39 on the ends thereof to prevent the cables from retracting entirely into the enclosure 28.

[0032] Referring to FIGS. 3 and 4, a user-variable resistance mechanism of the device 10 includes independent brake drums 70, 72, located between the first and second portions 44, 46 of the frame 43, which along with other components described here, provide user-variable resistance to the withdrawal of the cords 36, 38 from a respective take-up reel 62, 64. Each brake drum 70, 72 is preferably rotationally interconnected to the respective axles 58, 60 by a one-way clutch mechanism (not shown), which is configured to engage only when the associated take-up reel unwinds. Thus, the resistance mechanism preferably only operates during withdrawal of the cords 36, 38.

[0033] Preferably, the one-way clutch mechanism comprises an annular bearing assembly (not shown) connected to each brake drum, which includes radially translating bearings which grip the associated axles 58, 60 only during withdrawal of the cable on the associated take-up reel, thereby rotationally interconnecting the brake drum and take-up reel only during withdrawal.

[0034] Rotation of the brake drums 70, 72 can be inhibited by the tensioning of a brake band 74 disposed between the first and second portions 44, 46 of the frame 43, which brake band 74 applies friction to the circumference of the drums. The brake band 74 partially encircles each drum 70, 72, contacting about ¾ of the circumference of each drum and is substantially equal in width to the brake drums 70, 72, with the edges of the band substantially aligned with the edges of the drums 70, 72. The brake band 74 is preferably formed of metal having a thickness of about 0.2 to 0.5 mm, a width of about 1⅜ inches, and a length of about 13-14 inches.

[0035] Tension in the brake band 74 is controlled by rotating external knob 76 which is connected to a threaded shaft 78, which shaft passes through a non-threaded hole 80 in a center portion 88 the brake band 74 which spans between the brake drums 70, 72. The axis of rotation of the shaft 78 is preferably substantially perpendicular to the axles 58, 60 about which the brake drums 70, 72 rotate, and substantially perpendicular to the top surface 51 of the base 12.

[0036] The shaft 78 also passes through a non-threaded hole 82 in a rigid U-shaped member 85, which U-shaped member is aligned with the opening thereof facing away from the center portion 88 of the brake band. Thus, in the normal orientation of the exercise device 10, arms 90, 92 of the U-shaped member 85 extend downwardly from a base 94 thereof. Opposite ends 84, 86 of the brake band 74 are fixedly connected to the arms 90, 92 of the U-shaped member 85 such that the brake band 74 and the inverted U-shaped member 85 form a contiguous loop.

[0037] A preferably rectangular threaded block 96 is engaged with the threads of the shaft 78. The threaded block 96 is closely received between the arms 90, 92 of the U-shaped member 85 and is closely received between the vertical portions 48, 55 of the first and second panels 44, 46 of the frame 43, which substantially prevent the rotation of the threaded block 96 about the shaft 78. Thus, when a user rotates the shaft 78, the threaded block 96 translates along the shaft.

[0038] A linear spring 97 is disposed around the shaft 78 between a top surface 98 of the threaded block 96 and a bottom surface 100 of the base 94 of the U-shaped member 85. Preferably, a bottom portion of the spring rests within an appropriately shaped recess in the block 96.

[0039] It can be appreciated that when a user rotates shaft 78 via control knob 76 in a first direction, the threaded block 96 moves towards the top of the device 10. More precisely, the block 96 moves toward the center portion 88 of the brake band 74. This movement of the block 96 urges the spring 97 against the U-shaped member 85 which tightens the brake band 74 around the drums 70, 72. Opposite rotation of the knob 76 and shaft 78 loosens the brake band.

[0040] Referring to FIG. 8, the threaded block 96 preferably includes recesses 170, 172 which closely receive the arms 90, 92 of the U-shaped member 85.

[0041] Referring to FIGS. 3, 6, and 7, downward movement of the threaded shaft 78 is prevented by a stop 104 which engages a portion of the frame 43, such as an enlarged portion of the shaft. Upward movement of the shaft 78 is prevented by the tension in the brake band 74. The shaft 78 includes a lower stop 106 which limits the downward movement of the threaded block 96. That is, the stop 106 establishes a predetermined maximum distance between the block 96 and the base 94 of the U-shaped member 85. Preferably, the maximum distance is less than the at-rest length of the linear spring 97 (plus the depth of any recess in which the spring sits) such that a predetermined amount of tension remains in the system when the tension control is in the loosest position, which serves to prevent undesirable “play” in the mechanism.

[0042] Referring to FIGS. 7 and 8, a predetermined maximum tension in the brake band 74 is established by providing an upper limit on the movement of the threaded block 96. The upper limit is established by stops 108, 110 which extend inwardly from the vertical panels 48, 55 of the first and second portions 44, 46 of the frame 43, which stops 108, 110 project inwardly a distance sufficient to contact the top surface 98 of the threaded block 96. Preferably, an outer radius of the linear spring 97 is less than a distance between the axis of the threaded shaft 97 and an inner endmost portion of the stops 108, 110 such that the stops 108, 110 do not contact or otherwise interfere with the movement of the spring 97.

[0043] Referring to FIG. 5, preferably the first portion 44 of the frame 43 includes an opening 99 through which the threaded block 96 is visible. The threaded block 96 includes a position indicator, such as a projection 101, visible through the opening 99. An outer surface 103 of the first portion 44 of the frame 43 includes a graduated scale (e.g., 0 . . . 10) to indicate the relative resistance provided by the device 10. Preferably, the position indicator is visible through an opening or transparent portion (not shown) of the enclosure.

[0044] Referring to FIG. 8, U-shaped member 85, threaded block 96, linear spring 97 and shaft 74 are substantially confined against lateral (i.e., horizontal in normal orientation) movement by, along one axis, the brake drums 70, 72, and, along a perpendicular axis, the vertical portions 48, 55 of the first and second portions 44, 46 of the frame 43. Referring to FIG. 4, the upper portion of the assembly (essentially the upper portion of the shaft 75) is confined against such movement by the frame 43 through which it passes.

[0045] Referring to FIGS. 2-4 and 9, each cable 36, 38 leading from each take-up reel 62, 64, preferably extends substantially vertically (i.e., substantially perpendicular to the base 12) through an annular bearing 112, 114 affixed to the frame 43. Each annular bearing 112,114 supports an idler pulley 116, 118, which is mounted for rotation with respect to the associated annular bearing about an axis substantially parallel to the base 12. Each annular bearing 112, 114 is mounted for rotation with respect to the frame 43 about an axis substantially perpendicular to the base 12. In addition to providing rotational support, the annular bearings 112, 114 provide guides through which the cables 36, 38 pass. Therefore, the annular interior surface of the bearings are preferably lined with friction- and wear-reducing material such as plastic, Teflon, or the like.

[0046] The idler pulleys 116, 118 are preferably mounted with an outer radial edge thereof flush with (i.e., substantially tangential to) an outer diameter 120 and top 122 of the associated annular bearing 112, 114. Further, an exit opening on the top portion 122 of each annular bearing 112, 114 is preferably eccentric to the axis of rotation of the bearing, such that the cords 36, 38 exit the associated annular bearing between the axis of rotation of the bearing (i.e., the center) and the associated idler pulley. In this manner, each annular bearing 112, 114 will tend to rotate to align the associated idler pulley 114, 118 with associated cord 36, 38 to provide smoother operation of the exercise device 10.

[0047] It should be noted that throughout the written description of this disclosure relative terms of orientation, such as top, bottom, front, rear, horizontal, vertical and the like are ordinarily intended to refer to the device as aligned in its most common orientation. That is, the orientation in which the base 12 is resting on a horizontal surface, such as the floor, with the base 12 aligned such that the annular bearings 112, 114 (discussed in detail below) are farthest away from the user. However, as can be appreciated, other orientations and configurations of the device 12 are contemplated in the present invention.

[0048] Referring to FIG. 11, in a first method of using the exercise device 10, a user secures the device in position by standing on the contact surfaces 24, 26 of the base 12 and adjusts the resistance control knob 76 to obtain the desired level of resistance. The user attaches the handles 130, 132 using the detachable clips 134 and performs any one of a variety of exercises on the arms, shoulders or back by repeatedly pulling the cable out of the cable control mechanism against the resistive force.

[0049] Each handle 130, 132 is preferably comprises of a tubular rigid portion (e.g., a hollow plastic tube) having grip disposed around the circumference. Flexible material (e.g., woven nylon, or the like) is connected to the rigid portion and includes and attachment point (e.g., a metal ring). Preferably the flexible material is a loop of material directed through the hollow tube. The handle is attached to a clip of the device via the attachment point.

[0050] Referring to FIG. 15, the exercise device 10 includes a multi-purpose accessory 176 in the form of a strap which can be attached around various body parts of the user, for example the arm, calf or thigh. Preferably the multi-purpose accessory 176 is a length of flexible material (e.g., woven nylon, or the like) about 20 in long and about 3 inches wide, with hook-and-loop fastening means affixed thereto. The multi-purpose accessory includes an attachment point suitable for attachment to a cable 36 (e.g., via the clip), which attachment point is preferably located on a center portion of the accessory.

[0051] Referring to FIG. 12, a foot attachment component 136 of the invention provides a stirrup-like means to attach the cables 36, 38 of the exercise device to a foot of the user. The foot attachment component 136 includes a heal portion 138, which partially encircles the heal of the user, and securing portion 140 which encircles the top and sole of the foot, substantially at right angles to the heal portion 138. The securing portion 140 is preferably formed of a strip of hook-and-loop fastening material 142 with a length of mating hook-and-loop fastening material 144 extending from one end 146 thereof. A loop 148 (e.g., a plastic loop) is affixed to an opposite end 149 thereof, which loop 148 receives the mating section of hook-and-loop material, which can be doubled-back upon the other section of the securing portion to affix the foot attachment component on the foot.

[0052] A first end 150 of the heal portion 138 of the foot attachment component is affixed at substantially a right angle to the securing portion 140 adjacent the loop 148 thereof. Another end 152 of the heal portion 138 is affixed (also at a right angle) to the securing portion 140 about 7 inches from the first end 150.

[0053] The foot attachment component 136 includes multiple points to which a cable from the exercise device 10 may be attached. These attachment points are preferably wear-resistant and can be in the form of metal rings, as shown. A first attachment point 154 is substantially at the center of the heal portion 138, such that when properly secured, the attachment point 154 is in alignment with the back of the foot. Second and third attachment points 156, 158 are located adjacent the locations where the first and second ends 150, 152 of the heal portion 138 and the securing portion 140 are affixed to one another, respectively. When properly secured the second and third attachment points 156, 158 are located on the lateral and medial sides of the foot, as shown.

[0054] In applying the foot attachment component 136, the user places the sole of the foot on the section of the securing portion 140 that is between the ends 150, 152 of the heal portion 138, with the heal portion 138 directed around and against the heal of the user. The mating section 144 of the securing portion 140 is then directed over the top of the foot, through the loop 148 and doubled over to securely engage with the complementary portion of the securing portion. When properly aligned the first, second and third attachment points 154, 156, 158 are then located on the back of the heal and the lateral and medial sides of the foot, respectively.

[0055] Referring to FIG. 13, in another method of the invention, the user lays on their side with an outside portion of one leg (e.g., the calf) resting on one of the contact surfaces 24, 26 of the device 10 to secure the device in place. One of the cords 36, 38 is connected to (preferably) the medial contact point 158 of the foot attachment component 136. The user raises the connected leg against the resistive force of the device 10 to perform the exercise.

[0056] Referring to FIG. 14, in another method of the invention employing the foot attachment component 136, the user connects one of the cords 36, 38 to (preferably) the first attachment point 154 and performs leg raises, knee raises, or the like, against the resistance force, while standing on the base 12 with the other leg to stabilize the device.

[0057] Referring to FIG. 16, in another method of the invention, the user connects one of the cords 36, 38 to (preferably) either the second or third attachment point 156, 158 and applies pressure to either the base handles 18, 20 or the contact surfaces 24, 26 to secure the device, while “on all fours.” Then the user extends the associated leg backward and upward against the resistive force.

[0058] In another method of the invention employing the foot attachment component 136, the user reclines on floor on their back, with their legs preferably vertical. Preferably each cable 36, 38 is attached to one of the foot attachment components 136, on either foot. The device 10 is placed on the floor adjacent the user, below the legs, preferably on one of the long edges of the base 12 such that the “top” surface of the device 10 is directed toward the user. Then the user performs leg extension or hip raise exercises, or the like against the resistive force provided by the device, while holding the device 10 down against the floor with their hands.

[0059] In yet another method of the invention employing the foot attachment component 136, the user reclines on the floor on their back with each cable 36, 38 attached to one of the foot attachment components 136, on either foot. The user holds the device 10 above their head, preferably with the base handles 18, 20 and performs bicycle exercises, or the like, against the resistive force.

[0060] In another method of the invention employing the handles 130, 132, the user sits on one of the contact surfaces 24, 26 of the base 12, preferably with their back facing the enclosure 28. The user grasps the handles 130, 132, with the associated cable 36, 38 directed behind the back of the user down to the cable control mechanism 30. The user then extends the cable 36, 38 against the resistive force.

[0061] In a further method of the invention employing the handles 130, 132, the user reclines on the floor on their back with their legs extended against the floor. The exercise device 10 is placed on the floor on a long edge of the base 12 such that the contact surfaces 24, 26 are facing the user and (preferably in contact with) the upturned soles of the feet of the user. The user grasps one or both of the handles 130, 132 attached to the cords 36, 38 and extends the cords from the device against the resistive force.

[0062] It can be appreciated that the cable exercise device constructed and used according to the present invention provides a compact, portable and inexpensive means to perform a large number of exercises with virtually all of the muscle groups of the body. It should be understood, of course, that the specific form of the invention herein illustrated and described is intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention. 

What is claimed:
 1. A portable exercise device, comprising: a base having a pair of contact surfaces suitable to receive the feet of a user; first and second retracting cables connected to said base; first and second means to rewind said first and second retracting cables from a withdrawn position, respectively; said first and second rewinding means being independent of one another; common means to adjust a resistance to the withdrawal of said first and second retracting cables, said common adjustable resistance means being adjustable by said user.
 2. A portable exercise device as in claim 1, wherein: said device further comprises first and second take-up reels associated with said first and second retracting cables, respectively; said common adjustable resistance means further comprises means to inhibit a rotation of said first and second take-up reels, only during withdrawal of said respective cables.
 3. A portable exercise device as in claim 2, wherein said common adjustable resistance means comprises: a brake drum associated with one of said first and second take-up reels; a brake band operable to contact said brake drum; means to rotationally interconnect said brake drum and said one take-up reel during withdrawal of an associated cable, said rotational interconnection means being inoperable during rewinding of said associated cable.
 4. A portable exercise device as in claim 3, wherein said rotational interconnection means comprises a one-way clutch.
 5. A portable exercise device as in claim 3, wherein said adjustable resistance means comprises: means to adjust a tension in said brake band, said tension adjustment means being adjustable between first and second positions; said tension in said brake band being controlled in part by an elastic means.
 6. A portable exercise device as in claim 5, wherein said elastic means reduces a change in tension in said brake band when said tension adjustment means is moved between said first and second positions, as compared to if said elastic means were inelastic.
 7. A portable exercise device as in claim 6, wherein said tension adjustment means has predetermined minimum and maximum tension positions and said elastic means is not in an at-rest position when said tension adjustment means is in either of said minimum or maximum tension positions.
 8. A portable exercise device as in claim 5, wherein, during rewinding, said elastic means permits loosening movement of a portion of said brake band adjacent said elastic means.
 9. A portable exercise device as in claim 5, wherein said tension adjustment means comprises: a threaded shaft operable to be turned by said user; a threaded block disposed on said threaded shaft; said threaded block imparting movement of said brake band via said elastic means.
 10. A portable exercise device as in claim 9, wherein said common adjustable resistance means comprises: first and second brake drums independently rotationally interconnected to said first and second take-up reels, by first and second one-way clutch means, respectively; said brake band being in contacting relation to both said first and second brake drums; first and second free ends of said brake band being connected to a rigid member; and said elastic means being disposed between said threaded block and said rigid member.
 11. A portable exercise device as in claim 10, wherein: said elastic means comprises a linear spring; said threaded shaft is directed through a hole in a portion of said brake band spanning between said first and second brake drums, through a hole in said rigid member, and through said linear spring.
 12. A method of exercising comprising: securing a portable exercise device by applying a user's weight to a base portion of said portable exercise device; withdrawing first and second independently retracting cables connected to said base against a common resistance means adjustable by said user; returning said first and second retracting cables to said base via first and second means to rewind said first and second retracting cables, said first and second means to rewind being independent of one another; and said common adjustable resistance means being independent of said first and second means to rewind and being inoperable during rewinding of said first and second retractable cables. 